The present invention relates to a continuous plating apparatus capable of continuously plating each workpiece transferred in a plating tank while supplying power to each workpiece.
In FIG. 9, workpieces 50 (50A to 50E) are thin sheet-shaped articles (e.g., printed circuit board material), and are continuously transferred in a plating tank 10P in a workpiece transfer direction (X) at constant intervals. A workpiece continuous transfer means includes a transfer rail (not shown) that is disposed above a workpiece transfer path and extends in the direction X, a plurality of sliders that are movably secured along the transfer rail (not shown; a portion that serves as a power supply path is indicated by 36P (36PA to 36PE)), a chain conveyer (not shown) that transfers each slider in synchronization, and the like.
Anodes 15PL and 15PR are commonly used for the workpieces (cathodes) 50A to 50E. The anodes 15PL and 15PR are disposed on either side (upper side or lower side in FIG. 9) of the workpiece transfer path, and extend in the direction X. The anodes 15PL and 15PR are connected to an anode terminal 21 of a power supply device 20P through a power supply cable 17P (17PL and 17PR). A cathode terminal 25 of the power supply device 20P is electrically connected to the workpieces 50A to 50E through a power supply cable 37P, the transfer rail, and the sliders (power supply paths 36PA to 36PE).
The power supply device 20P has a capacity sufficient to supply a set current value (e.g., 1 A/dm2) to sides Fr and Fl of each workpiece 50, and is driven by constant current control. The workpieces 50A to 50E can thus be continuously plated while continuously supplying power to the workpieces 50A to 50E transferred in the plating tank 10P. For example, JP-A-2000-226697 discloses a constant current density profile at the middle way in the plating tank (see FIG. 3B).
The electrical resistance and the electrode-electrode distance vary corresponding to each workpiece due to the structure of the electrical path (e.g., cable 17P (17PL and 17R) or power supply path 36P (36PA to 36PE)) or assembly. This causes the following problems. Specifically, a variation in the thickness of the coating or the process quality may occur. The thickness of the coating or the process quality may differ between one side (first side) and the other side (second side) of a single workpiece. The thickness of the coating cannot be caused to differ corresponding to each workpiece. The thickness of the coating cannot be caused to differ corresponding to each side of a single workpiece. When further uniformity in the thickness of the coating and the process quality are desired, the thickness of the coating and the process quality must be made uniform along the workpiece transfer direction (front, center, and rear).